NEW YORK — Since Mikhail Prokhorov and Jay-Z became the faces of the Brooklyn Nets, the objectives of their mission have been made abundantly clear: Become relevant, move to Brooklyn, be better than the Knicks, steal the market. General manager Billy King made the deals and Prokhorov wrote the checks. The Nets embarked on an unprecedented spending spree this past summer and not only retained Deron Williams, but also surround him with some capable talent. Clearly, they are relevant. And yes, they are